<> Navigation: * [[AJMPublic/camcasp|CamCASP main page]] = The ENERGY-SCAN module = In CamCASP it is possible to compute the first-order energies $E^{(1)}_{\rm elst}$ and $E^{(1)}_{\rm exch}$ for a large number of dimer configurations without repeating the wavefunction calculation on the monomers. This is possible only because the first-order energies can be accurately evaluated in a monomer basis set, that is, without the presence of the mid-bond and far-bond functions that are necessary for converging the second-order interaction energy components. In this tutorial we will cover how these energies can be computed using the ENERGY-SCAN module, and additionally, how the distributed density-overlap integrals can be computed. {{{#!wiki important Important '''Reference Geometries''' The energy scan with module ENERGY-SCAN works on the principle that we computer the molecular orbitals and energies for the molecule in their '''reference''' orientations, and then rotate/translate them as needed to compute the interaction energies for the interacting dimer. Consequently, it is important that this '''reference''' orientation must be used to define all molecules in the CamCASP command files. }}} {{{#!wiki important Important //Integral Accuracy//: When the DF is done accurately - here when the DC-aux basis is used - then it seems that we must use 1-electron integrals computed as accurately as is possible. So we use ''Integral switch = 1''. But if we use a relatively poor DF (as is the case with the MC-MC case when we use the MC-aux basis type), then we need to rely on an error cancellation in the terms that appear in $E^{(1)}_{\rm elst}$. So we need to use ''Integral switch = 0''. }}} == Commands in ENERGY-SCAN == [[attachment:ENERGY-SCAN commands]] {{{ BEGIN SCAN/ENERGY-SCAN {PROBE || SCAN} [molecule || atom] +++ WITH [ [[and] CHARGE ]] UNITS [A || ANG || ANGSTROM || BOHR || AU || A.U.] +++ [DEG || DEGREE || DEGREES || RAD || RADIAN || RADIANS] NOTE: UNITS must come before POINTS/RANDOM CENTRE/CENTER PROBE [on] [COM]/[XYZ ] REGULARIZE [E1] [[and] E2] [with] ETA [=] {ENERGIES || ENERGY} [DISP/DISPERSION/E2DISP] +++ [&/and/,] [IND/INDUCTION/E2IND] [&/and/,] [ELST/E1ELST/ELECTROSTATICS] +++ [&/and/,] [E1EXCH] [&/and/,] [E2EXIND] & [E2EXDISP] & [OVERLAP] [NOTHING] LATTICE POINTS [TRANSLATIONS || TRANSLATIONS-ONLY] [SKIP-FIRST-COLUMN] x1 y1 z1 [angle1 nx1 ny1 nz1] x2 y2 z2 [angle2 nx2 ny2 nz2] etc --- <----end POINTS block with three hyphens. RANDOM POINTS [=] DRMIN [=] DRMAX [=] RADIAL [points] [=] SKIP [=] [angular] [configurations] WRITE [APPEND] --- ENERGY-FILE [PREFIX] [[in || using] STYLE